Method of delivering oxygen to basic oxygen furnaces, and oxygen lances therefor



March 14, 1967 1.. H. HUTTON METHOD OF DELIVER ING OXYGEN TO BASIC OXYGEN FURNACES AND OXYGEN LANCES THEREFOR Filed May 5, 1965 5 Sheets-Sheet 1 IIIIII M I I! fT- TT I I I I I I I I I I l I INVENTOR LELAND H. HUTTQN EZ/Q fi l/mmy ATTORNEYS March 14, 1 967 H. HUTTON 3,309,195

METHOD OF DELI ING OXYGEN TO BASIC OXYGEN FURNACES AND OXYGEN LANGES THEREFOR Filed May 5, 1965 5 Sheets-Sheet 2 INVENTOR.

LE LAN D H. HUTTON ATTORNEYS March 14, 1967 L. H. HUTTON 3,

METHOD OF DELIVERING OXYGEN TO BASIC OXYGEN FURNACES, AND OXYGEN LANCES THEREFOR 5 SheetsSheet 3 Filed May 5, 1965 INVENTOR- LELAND H. HUTTON BY l ag W.

ATTORNEYS March 14, 1967 L H. HUTTON 3,309,195 7 METHOD OF DELIVEZRING OXYGEN TO BASIC OXYGEN FURNACES, AND OXYGEN LANCES THEREFOR Filed May 5, 1965 5 Sheets-Sheet 4 I I I2 INVENTOR LELAN D H. HUTTON ATTORNEYS March 14, 1967 H. HUTTON 3,309,195

METHOD OF DELIVERING OXYGEN TO BASIC OXYGEN FURNACES, AND OXYGEN LANCES THEREFOR Filed May 5, 1965 5 Sheets-Sheet 5 INVENTOR.

LELAN D H. HUTTON M WW' ATTORNEYS United States 3,309,195 Patented Mar. 14, 1967 3,309,195 METHOD OF DELIVERING OXYGEN T BASIC OXYGEN FURNACES, AND OXYGEN LANCES THEREFOR Leland H. Hutton, University Heights, Ohio 44106 Filed May 5, 1965, Ser. No. 453,398 16 Claims. (Cl. 75-60) This application is a continuation-in-part of my copending applications, Ser. No. 379,546, filed July 1, 1964, and Ser. No. 379,576, filed July 1, 1964.

This invention relates generally to the manufacture of steel in basic oxygen furnaces, but has reference more particularly to a novel method of delivering oxygen to such furnaces, and to lances or nozzles used therefor.

The aforesaid patent applications are directed to watercooled oxygen lance nozzles or tips, in which three circumferentially spaced oxygen passages are employed, which are inclined at an angle of about 10 degrees to the axis of the nozzle or tip.

I have found that the use of such nozzles in the manufacture of steel in basic oxygen furnaces is productive of results which were not entirely recognized at the time of the filing of said applications, and that certain improvements in the contours and arrangement of the oxygencarrying passageways have led to even better results.

More particularly, I have found that by restricting the overall diameter of the oxygen lances to a range of from about to 12 inches, and utilizing a plurality of oxygencarrying passageways in the nozzles which are, in effect, Venturi tubes, inclined to the axisof the nozzle at an angle of from about 7 to about 12 degrees, I have been able to achieve through the use of such nozzles the following results:

(a) An increase in the speed of oxygen flow through the nozzle up to an average speed which is twice the speed of sound, i.e., Mach 2.

(b) A sharp control of the direction, volume, and pattern of penetration of the expanding oxygen.

(c) A speeding up or acceleration of the process and an increase in the yield of steel.

(d) A reduction in the splattering of molten steel and slag in the bath, with consequent increase in the life of the refractory lining of the furnace, decrease in skull build-up at the top of the furnace, and a general reduction, in the cost of maintenance of the furnace, hood, and other equipment used in the basic oxygen process.

The present invention, accordingly, is directed to a method of and means for accomplishing or attaining the aforesaid results, and will be described more particularly with reference to the accompanying drawings, forming a part of this application and wherein FIG. 1 illustrates somewhat diagrammatically the use of oxygen lances in accordance with the present invention in the manufacture of steel by the basic oxygen process;

FIG. 2 is a fragmentary cross-sectional view of one form or type of oxygen lance embodying the invention;

FIG. 3 is an end elevational view of the lance of FIG. 2, as viewed from the right end of said figure;

FIG. 4 is a cross-sectional view, taken on the line 4-4 of FIG. 2;

FIG. 5 is a cross-sectional view, taken on the line 5-5 of FIG. 2;

FIG. 6 is a cross-sectional view, taken on the line 6-6 of FIG. 2;

FIG. 7 is a plan view of the collar tion of the lance;

FIG. 8 is a cross-sectional view, taken on the line 8-8 of FIG. 7;

FIG. 9 is a view similar to FIG. 2, but showing a modified form of lance;

steel making and segment porreference numeral FIG. 10 is an end elevational view of the lance of FIG. 9, as viewed from the right end of said figure;

FIG. 11 is a cross-sectional view, taken on the line 11-11 of FIG. 9, and

FIG. 12 is a cros-sectional view, taken on the line 12-12 of FIG. 9.

In FIG. 1 there is illustrated a furnace 1 of a conventional type, such as is commonly used for the manufacture of steel by the basic oxygen process.

The furnace 1 is mounted on trunnions (not shown), but the axis of which is indicated by reference numeral 2, so that the furnace may be tilted to empty the same at the conclusion of the steel-making operation.

The bath line or level within the furnace is indicated by reference numeral 3.

The furnace 1 is conventionally lined with high magnesia tar bonded brick, indicated by reference numeral 4.

A hood, fragmentarily indicated by reference numeral 5 is disposed above the top of the furnace 1 for the purpose of receiving the products of combustion.

In the steel-making operation, an oxygen lance 6, which is aligned axially with the furnace, is moved downwardly to a position such that its lower end is disposed at a distance of from 50 to 55 inches from the bath line or level 3, and oxygen is blown through the lance in a predetermined volume, and at a predetermined pressure sufiicient to produce steel of desired quality in the furnace.

At the conclusion of the steel making operation, the lance 6 is raised to a height such that the furnace 1 may be tilted and its contents emptied into a ladle or similar vessel.

When an oxygen lance is used having a single axial passage for the oxygen in the nozzle or tip of the lance, the pressures necessary to produce steel in the furnace 1 are such as to cause the molten steel to splatter on the sides of the furnace and to form a skull, indicated by 7, on the top of the furnace.

In patents, such as Patents Nos. 2,807,506, 2,878,115, 2,979,270 and 3,020,035, attempts have been made to utilize oxygen lances having a plurality of circumferentially-spaced inclined passageways, for the purpose of obtaining a better distribution of the oxygen, but in all cases, the use of such nozzles has been confined to open-hearth furnaces, wherein the bath area and distance from the nozzles to the walls of the furnace are sufliciently great that no problem of skull formation exists.

However, in the basic oxygen furnace process, the dimensions of the furnace are such that the bath area is relatively small and the walls of the furnace relatively close to the oxygen nozzle, so that the matter of nozzle design and distribution of oxygen by the nozzle becomes extremely important, if splattering and skull formation are to be minimized or avoided.

The oxygen lances and nozzles disclosed in my aforesaid pending applications have been found to be extremely beneficial for the purpose of reducing splattering and the formation of skull in basic oxygen furnaces, but, as hereinafter discussed, the lances and nozzles which are to be described hereinafter embody improvements in design which produce even more and greater beneficial effects when used in the basic oxygen furnace process.

Referring to FIGS. 2 to 8 inclusive of the drawings, there is disclosed the fragmentary lower portion of an oxygen lance consisting of tubular steel members 10, 11 and 12, in concentric spaced relation to each other, with the lower end of the member 10 at a higher level than the lower end of the member 11, and the lower end of the member 12 at a lower level than the lower end of the member 11.

Secured to the lower end of the member 10, as by welding 13, is a reducer 14 having a constricted lower portion 15, to the lower end of which there is secured, as

by welding 16, a tip or nozzle 17, preferably made as a casting or forging of copper, which is 99.5% pure and is free from occluded oxygen.

The tip or nozzle 17 has an upper conical external wall 18, a conical external Wall 19 extending below the wall 18 at a greater inclination to the axis of the nozzle than the wall 18, and a conical external wall 20 which extends below the wall 19 at a greater inclination to the axis of the nozzle than the wall 19.

Below the wall 20, the nozzle is provided with an upwardly extending annular flange 21, which coacts with the wall 20 to provide an annular trough 22.

The lower end of the tubular member 12 is welded to the upper end of flange 21, as at 23.

The tip or nozzle 17 is provided in its upper end with a central conical recess 24, from which a series of outwardly inclined passageways 25 extend downwardly through the nozzle, communicating the constricted portion of the reducer 14 with the space below the nozzle or tip. Three such passageways are shown, the axes of which are spaced apart circumferentially 120 degrees.

The axes of these passageways 25 are inclined at an angle of 10 degrees to the axis of the nozzle or tip 17.

Each passageway 25 constitutes, in effect, a Venturi tube, which consists of two truncated cones 26 and 27 connected at their smaller ends by a short cylinder or Venturi throat 28. The function of these Venturi tubes or passageways will be presently described. The walls of the cones 26 and 27 are inclined at an angle of 5 degrees to the wall of the throat 28, that is to say, to the axis of the passageway 25, and the nozzle or tip has a conical end face 29, which is substantially perpendicular to the axes of the passageways.

The tip or nozzle 17 is also provided with a series of circumferentially-spaced passageways 30, which are arranged alternately with the passageways 25 and extend downwardly and inwardly from the wall toward the center of the tip, the inner ends of these passageways communicating with each other. The axes of the passageways 30 are inclined at an angle of approximately 70 degrees to the axis of the tip or nozzle.

The tip or nozzle 17 is further provided with a series of circumferentially-spaced passageways 31, also arranged alternately with the passageways and extending downwardly and inwardly from the walls 18 and 19, the inner ends of these passageways communicating with the passageways at points 32 adjacent the inner ends of the latten, The passageways 31 are of slightly lesser diameter than the passageways 30, and the axes of the passageways 31 are inclined at an angle of approximately degrees to the axis of the tip or nozzle 17.

Secured to the wall 20 of the nozzle, as by welding, are three circumferentially-spaced arcuate segments 33.

Each of the segments 33 is disposed just below the inlet end of a passageway 31, and extends 36 degrees horizontally about the nozzle, that is to say, it extends 18 degrees horizontally from each side of a vertical plane which passes through the axes of each pair of associated passageways 39 and 31.

The segments 33 are preferably cut. from a ring, the outer surface of which corresponds with the inclined outer surface 34 of the segment 33, and since the segments are 36 segments, as a practical matter, ten such segments can be cut from a single ring of thhe dimension referred to.

Secured to the lower end of the tubular member 11, as at 35, is a conical collar 36 which bears against and extends downwardly below the outer surfaces 34 of the segments 33 and to a point 37 which is in spaced relation to the bottom of the trough 22.

Circumferentially-spaced portions of the collar 36 are removed, to provide recesses, the upper edges of which are indicated by reference numerals 38 and the side edges of which are indicated by reference numerals 39 and til.

The edges 38 of the collar are welded to the segments 33, as shown in FIG. 2, and the edges 39 and 40 of the recesses are in vertical planes which are coplanar with the ends of the segments 33.

In the use of the oxygen lance, as thus described, oxygen is supplied to the tubular member or conduit 10, and thence through the reducer 14 and passageways 25 to the top of the molten metal bath 3 in the basic oxygen furnace 1.

As oxygen is thus supplied to the bath, water for cooling the tip or nozzle 17 is supplied continuously to the space 41 between the nozzle 17 and the member 11, the water circulating downwardly to the annular trough 22 and then upwardly through the space 42 between the members 11 and 12.

A portion of the water in the space 41 strikes the upper surfaces of the segments 33, which thus constitute bafiies, and is diverted by these baffles through the passageways 31, thence through passageways 30, and outwardly into the space below the segments, where it mingles with the water which passed directly into the trough 22.

The conjoint action of the water passing directly into the trough 22 and that diverted through the nozzle and then into the trough produces a desired turbulence or flow of the circulating water which is highly effective to .produce an efficient cooling of the nozzle, maintaining the nozzle at a non-destructive temperature throughout long periods of use.

The cooling action is further enhanced by the fact that the cooling water takes a somewhat circuitous path in passing through the passageways 31 and 30, which passageways conjointly have a large cubical volume.

Furthermore, the spaces between the segments 33 act as passageways or channels to direct the cooling water directly into the trough 22, and this, also, has been found to be effective in producing an efficient, desired, cooling of the nozzle.

A highly important and extremely sigificant feature of the invention resides in the fact that the passageways 25 are, in effect, Venturi tubes or passageways, consisting of two truncated cones 26 and 27 connected at their smaller ends by the short cylinder or Venturi throat 28. This construction or configuration of the passageways, combined with the fact that the passageways are inclined downwardly and outwardly at a substantial angle to the axis of the nozzle, produces the following effects.

The cones 26 constrict the flow of the oxygen in such a manner, that it enters and passes through the throats 28 at an extremely high speed or velocity, which, in many cases, exceeds the speed of sound. After passage of the oxygen through the throats 28, the oxygen pressure is relieved, due to flaring of the cones 27, so that the oxygen rapidly expands, and by the time the oxygen reaches the bath, the oxygen is effective to react with the bath.

As a result, a sharp control of the direction, volume and pattern of penetration of the expanding oxygen is obtained, which not only accelerates the steel making process and increases the yield of steel, but reduces the splattering of molten metal and slag in the bath, thereby increasing the life of the refractory lining of the furnace, decreasing the skull build-up at the top of the furnace, and generally reducing the cost of maintenance of the furnace, hood, and other equipment.

In the use of a nozzle of the character described, having an outside diameter of 8.625", and passageways 25, in which the throat 23 has a length of and a diameter of 1.625", it was possible to produce a heat of steel in record time, utilizing a maximum flow of oxygen of 16,000 cubic feet per minute, and a maximum flow of cooling water of 660 gallons per minute.

Although the nozzle which has been described has three circumferentially-spaced passageways, any number of passageways, from 2 to 6, may be used, with consequent changes in spacing, dimensions of passageways, and

inclination of the passageways, while producing the improved results which have been described.

In FIGS. 9, 1O, 11 and 12, a modification of the nozzle is illustrated, in which a central passageway is provided in the nozzle for the introduction to the bath of an auxiliary gas or other desired additions to the bath.

For this purpose, the design of the nozzle, while essentially similar to that already described, is changed in some respects, necessitating the following description.

The lance consists of tubular steel members 50, 51 and 52 in concentric spaced relation to each other, with the lower end of the member 50 at a higher level than the lower end of the member 51, and the lower end of the member 52 at a lower level than the lower end of the member 51.

Secured to the lower end of the member 50, as by welding 53, is a reducer 54 having a constricted lower portion 55, to the lower end of which there is secured, as by welding 56, a tip or nozzle 57, preferably made as a casting or forging of copper, which is 99.5% pure and is free from occluded oxygen.

The tip or nozzle 57 has an upper conical external wall 58, and a conical external wall 59 extending below the wall 58 at a greater inclination to the axis of the nozzle than the wall 58.

Below the wall 59, the nozzle is provided with an upwardly extending annular flange 60 which coacts with the wall 59 to provide an annular trough 61.

The lower end of the tubular member 52 is welded to the uuper end of flange 60, as at 62.

The tip or nozzle 57 is provided in its upper end with a central conical recess 63 from which a series of outwardly inclined passageways 64 extend downwardly through the nozzle, communicating the constricted portion 55 of the reducer 54 with the space below the nozzle or tip. Three such passageways are shown, the axes of which are spaced apart circumferentially 120 degrees.

The axes of these passageways 64 are inclined at an angle of about degrees to the axis of the nozzle.

Each passageway 64 constitutes, in effect, a Venturi tube, which consists of two truncated cones 65 and 66, connected at their smaller ends by a cylinder or Venturi throat 67, which function in a manner similar to that described with reference to the passageways 25 of the previously described form of nozzle. The walls of the cones 65 and 66 are inclined at an angle of 5 degrees to the wall of the throat 67, that is to say, to the axis of the passageway 64, and the nozzle or tip has a conical end face 68, which is substantially perpendicular to the axes of the passageways.

The tip or nozzle 57 is also provided with a series of circumferentially-spaced passageways 69, which are arranged alternately With the passageways 64 and extend downwardly and inwardly from the wall 59 toward the center of the tip, but terminating at a point 70 which is spaced from the axis of the nozzle. The axes of the passageways 69 are inclined at an angle of approximately 70 degrees to the axis of the tip or nozzle.

The tip or nozzle 57 is further provided with a series of circumferentially-spaced passageways 71, also arranged alternately with the passageways 64 and extending downwardly and inwardly from the walls 58 and 59, the inner ends of these passageways communicating with the pas-' sageways 69 at point 72 adjacent the inner ends of the latter. The passageways 71 are of slightly lesser diameter than the passageways 69, and the axes of the passageways 71 are inclined at an angle of approximately 60 degrees to the axis of the nozzle or tip 57.

Secured to the wall 59 of the nozzle, as by welding, are three circumferentially-spaced arcuate segments 73.

Each of the segments 73 is disposed just below the inlet end of a passageway 71, and extends 36 degrees horizontally about the nozzle, that is to say, it extends 18 degrees horizontally from each side of a vertical plane which passes through the axes of each pair of associated passageways 69 and 71. Each of the segments has an inclined outer surface 74.

Secured to the lower end of the tubular member 51, as at 75, is a conical collar 76, which bears against and extends downwardly below the outer surfaces 74 of the segments 73 and to a point 77 which is in spaced relation to the bottom of the trough 61.

Circumferentially-spaced portions of the collar 76 are removed to provide recesses, the upper edges of which are indicated by reference numeral 78, and the side edges of which are indicated by reference numerals 79 and (see FIG. 12). The edges 78 of the collar are Welded to the segments 73, as at 81, and the edges 79 and 80 of the recesses are in vertical planes which are coplanar with the ends of the segments 73.

Extending axially through the nozzle 57, from the conical recess 63 to the lower end of the nozzle, is a passageway 82 having a flared lower end 83.

In the use of the oxygen lance, as thus described, oxygen is supplied to the tubular member or conduit 50, and thence through the reducer 54 and passageways 64 to the top of the molten metal bath 3 in the basic oxygen furnace 1.

As oxygen is thus supplied to the bath, water for cooling the tip or nozzle 57 is supplied continuously to the space 84 between the nozzle 57 and the member 51, the water circulating downwardly to the annular trough 61 and then upwardly through the space 85 between the members 51 and 52.

A portion of the water in the space 84 strikes the upper surfaces of the segments 73, which thus constitute baffies, and is diverted by these baflies through the passageways 71, thence through passageways 69 and outwardly into the space below the segments, where it mingles with the water which passed directly into the trough 61.

The conjoint action of the water passing directly into the trough 61 and that diverted through the nozzle and then into the trough produces a desired turbulence or flow of circulating water which is highly effective to produce an efiicient cooling of the nozzle, maintaining the nozzle at a non-destructive temperature throughout long periods of use. I

The cooling action is further enhanced by the fact that the cooling water takes a somewhat circuitous path in passing through the passageways 71 and 69, which passageways conjointly have a large cubical volume.

Furthermore, the spaces between the segments 73 act as passageways or channels to direct the cooling water directly into the trough 61, and this, also, has been found to be effective in producing an efiicient, desired, cooling of the nozzle.

The operation and use of the nozzle thus described is substantially the same as described in connection with FIGS. 2 to 8 inclusive, but in this case, the axial passageway 82-83 is utilized to feed an auxiliary gas or other additives to the bath during the steel making process.

Having thus described my invention, I claim:

1. In a method of producing steel in a basic oxygen furnace, the steps which comprise inserting an oxygen lance into the furnace substantially perpendicularly to the bath level in the furnace, with the nozzle of the lance at a predetermined point above the level of the bath, and flowing oxygen through the lance while causing the oxygen to pass through a plurality of Venturi passageways in the lance nozzle disposed at an angle of from 7 to 12 degrees to the axis of the nozzle, whereby a desired pattern of penetration of oxygen into the steel is provided.

2. The method, as recited in claim 1, in which cooling water is circulated through the nozzle continuously during the steel-making process.

3. The method, as recited in claim 2, wherein the nozzle is of conical form, and the passageways are characterized by the fact that they comprise two truncated cones connected at their smaller ends by a cylindrical throat.

4. The method, as recited in claim 3, wherein auxiliary gas is passed through the nozzle axially thereof.

5. In a method of producing steel in a basic oxygen furnace, the steps which comprise disposing an oxygensupplying nozzle or tip above the center of the metal bath in the furnace, at a distance of from about 50 to 55 inches above the bath level, and blowing oxygen through Venturi passageways in the nozzle disposed at an angle of from about 7 to about 12 degrees to the axis of the nozzle, whereby a desired pattern of penetration. of oxygen into the steel is effected, and splattering of steel and slag in the furnace is reduced.

6. The method, as recited in claim 5, wherein an auxiliary gas is passed axially through the nozzle.

7. In an oxygen lance for making steel in a basic oxygen furnace, three concentrically arranged tubular members, the innermost of which is adapted for the passage of oxygen therethrough, and the others adapted for the passage of a cooling fluid therethrough, a nozzle or tip in communication with the innermost member, said nozzle or tip made of a single piece of copper, having a plurality of circumferentially-spaced oxygen-carrying passageways extending therethrough at an inclination of from about 7 to about- 12 degrees to the axis of said nozzle.

8. An oxygen lance, as defined in claim 7, wherein each of said passageways is a Venturi tube, consisting of truncated cones joined at their smaller ends by a cylindrical throat.

9. An oxygen lance, as defined in claim 8, wherein the overall diameter of said nozzle is from about 5 to about 12 inches.

10. An oxygen lance, as defined in claim 7, wherein said nozzle is provided with circumferentially-spaced passageways arranged alternately with said first-named passageways, and extending into the nozzle toward the axis of the nozzle, said second-named passageways adapted for the passage of a cooling fluid therethrough.

11. In an oxygen lance of the character described, a nozzle made of a single piece of copper having a plurality of circumferentially-spaced oxygen carrying passageways extending therethrough at an inclination of from about 7 to about 12 degrees to the axis of the nozzle.

12. An oxygen lance, as defined in claim 11, wherein each of said passageways is a Venturi tube, consisting of truncated cones joined at their smaller ends by a cylindrical throat.

13. An oxygen lance, as defined in claim 12, wherein the overall diameter of said nozzle is from about 5 to about 12 inches.

14. An oxygen lance, as defined in claim 11, wherein said nozzle is provided with circumferentially-spaced passageways arranged alternately with said first-named passageways, and extending into the nozzle toward the axis of the nozzle, said second-named passageways adapted for the passage of a cooling fluid there-through.

15. In a method of producing steel in a basic oxygen furnace, the steps which comprise inserting an oxygen lance into the furnace substantially perpendicularly to the bath level in the furnace, with the nozzle of the lance at a predetermined distance above the level of the bath, and flowing oxygen through the lance while causing the oxygen to pass at supersonic speed through a plurality of circumferentially-spaced Venturi passageways, each consisting of two truncated cones connected at their smaller ends by a cylindrical throat which is relatively short as compared with the length of the cones, said Venturi passageways being disposed at an angle of from 7 to 12 degrees to the axis of the nozzle, whereby a desired penetration of oxygen into the steel is provided, and splattering of steel and slag against the furnace side wall is avoided.

16. An oxygen lance for making steel in a basic oxygen furnace, three concentrically arranged tubular members, the innermost of which is adapted for the passage of oxygen therethrough, and the others adapted for the passage of a cooling fluid therethrough, a nozzle or tip in communication with the innermost of said members, said nozzle or tip made of a single piece of metal having a plurality of circumferentially-spaced oxygen-carrying Venturi passageways, each consisting of two truncated cones connected at their smaller ends by a cylindrical throat which is relatively short as compared with the length of the cones, said Venturi passageways being disposed at an angle of from 7 to 12 degrees to the axis of the nozzle.

References Cited by the Examiner UNITED STATES PATENTS BENJAMIN HENKIN, Primary Examiner. 

1. IN A METHOD OF PRODUCING STEEL IN A BASIC OXYGEN FURNACE, THE STEPS WHICH COMPRISE INSERTING AN OXYGEN LANCE INTO THE FURNANCE SUBSTANTIALLY PERPENDICULARLY TO THE BATH LEVEL IN THE FURNACE, WITH THE NOZZLE OF THE LANCE AT A PREDETERMINED POINT ABOVE THE LEVEL OF THE BATH, AND FLOWING OXYGEN THROUGH THE LANCE WHILE CAUSING THE OXYGEN TO PASS THROUGH A PLURALITY OF VENTURI PASSAGEWAYS IN THE LANCE NOZZLE DISPOSED AT AN ANGLE OF FROM 7 TO 12 DEGREES TO THE AXIS OF THE NOZZLE, WHEREBY A DESIRED PATTERN OF PENETRATION OF OXYGEN INTO THE STEEL IS PROVIDED. 